Outliers is an interesting concept. I think Keith is correct in reminding us that the people who reached that degree of accomplishment were outliers themselves. While there are some "traditionalists" who go on and on about loyalty and such, it is worth considering that the men under discussion here, Takeda, Sagawa and Ueshiba. trained mostly on their own. Each was noted for comments like "I personally developed past" (insert name) "I discovered" such and such "My aiki is different than"....
Each was a trail blazer, each was contentious in their own way, stubborn, and very much fit the model of individual genius, where the work led them down their own twisting paths. Interestingly enough some would call that research and turning down different paths as "flighty." Personally, I have never considered a fox hound on a trail turning left and right and leaving the trail all together, along with the followers behind, as "flighty."
He was the only one who never lost site of the goal.

For that reason, I don't think it is possible to become that good within a system in the first place-that is if you a know a system that can produce these men. Note again, in the interview quoted in Peter's article that, Ueshiba (Just like Takeda, Sagawa, and many of the historical figures before them) was known for going off and training solo. Where did a system support those discoveries?

When it comes to weapons and aiki, I believe most of these discussions are off-base when it comes to what that means and how to do it; traditional or modern, no matter. Most discussions come down to power and technique, or evasion in movement (which is a non starter and misses the mark all together). When it comes to power, these men were intimate with it and its uses in ways most martial artists will never achieve or even hope for, they openly discussed power. Why did they ignore it many discussions of weapons and revert to aiki?

Anyway, in regards to their training, the requirements that would support that degree of accomplishment are not in a system, are not developed in any group setting, and are not expressed in any Japanese environment I can think of that would welcome it.
Example: How would a kyu ranked person, who has the skills that Takeda, Sagawa and Ueshiba were talking about, work in a Shihan's own dojo, when the reality is they are better than the Shihan? Result...outlier.

I don't think "outliers" in the martial arts is an accurate use of the term. Martial arts exist as systems; you rate or average out people within systems. Outliers have always had a tendency to create systems of their own; either be choice or by default they simply don't "fit-in" to a system, and usually garner support of their own as they wander off the trail..... in pursuit of the fox.
Regards
Dan